Added support for HDMI 3D Stereo with Quadro Kepler and later GPUs. See
the documentation for the "Stereo" X configuration option in the README for
details.

Added experimental support for OpenGL threaded optimizations, available
through the __GL_THREADED_OPTIMIZATIONS environment variable. For more
information, please refer to the "Threaded Optimizations" section in chapter
"Specifying OpenGL Environment Variable Settings" of the README.